php生成缩略图的更能，遇到点有关问题

php生成缩略图的更能，遇到点问题，请教各位
想实现一个上传图片并生成缩略图的功能，从网上找了断代码，也成功了。
想一次生成两张――一张大缩略图，一张小缩略图，结果就提是下面的代码：

Notice: Undefined variable: RESIZEWIDTH in D:\WWW\qiangyuan\up.php on line 17
Notice: Undefined variable: RESIZEWIDTH in D:\WWW\qiangyuan\up.php on line 23



源程序代码如下：

//****************************************
//生成缩略图========================================

function ResizeImage($im,$maxwidth,$maxheight,$name){
$width = imagesx($im);
$height = imagesy($im);
if(($maxwidth && $width > $maxwidth) || ($maxheight && $height > $maxheight)){
if($maxwidth && $width > $maxwidth){
$widthratio = $maxwidth/$width;
$RESIZEWIDTH=true;
}
if($maxheight && $height > $maxheight){
$heightratio = $maxheight/$height;
$RESIZEHEIGHT=true;
}
if($RESIZEWIDTH && $RESIZEHEIGHT){
if($widthratio < $heightratio){
$ratio = $widthratio;
}else{
$ratio = $heightratio;
}
}elseif($RESIZEWIDTH){
$ratio = $widthratio;
}elseif($RESIZEHEIGHT){
$ratio = $heightratio;
}
$newwidth = $width * $ratio;
$newheight = $height * $ratio;
if(function_exists("imagecopyresampled")){
$newim = imagecreatetruecolor($newwidth, $newheight);
imagecopyresampled($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
}else{
$newim = imagecreate($newwidth, $newheight);
imagecopyresized($newim, $im, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
}
ImageJpeg ($newim,$name . ".jpg");
ImageDestroy ($newim);
}else{
ImageJpeg ($im,$name . ".jpg");
}
}

$FILENAME="product/min/".date("YmdHis"); //小图片文件名
$RESIZEWIDTH=150; // 生成图片的宽度
$RESIZEHEIGHT=113; // 生成图片的高度



if(isset($_FILES['image']['size'])){
if($_FILES['image']['type'] == "image/pjpeg"){
$im = imagecreatefromjpeg($_FILES['image']['tmp_name']);
}elseif($_FILES['image']['type'] == "image/x-png"){
$im = imagecreatefrompng($_FILES['image']['tmp_name']);
}elseif($_FILES['image']['type'] == "image/gif"){
$im = imagecreatefromgif($_FILES['image']['tmp_name']);
}


if($im){
if(file_exists("$FILENAME.jpg")){
unlink("$FILENAME.jpg");
}

ResizeImage($im,$RESIZEWIDTH,$RESIZEHEIGHT,$FILENAME); //生成小图
ResizeImage($im,600,450,"product/max/".date("YmdHis")); //生成大图
ImageDestroy ($im);
}
}

//****************************************
?>












------解决方案--------------------
在函数入口处对$RESIZEWIDTH 和 $RESIZEHEIGHT 赋初值

function ResizeImage($im,$maxwidth,$maxheight,$name){
$RESIZEWIDTH = $RESIZEHEIGHT = false;
....